[microjim]

Cool! What didn’t occur to me until I learnt it was that you get a multiplicative benefit with energy density when weight is a major factor (air transport, especially) because you need to spend less energy accelerating mass used by the battery itself.

[mcapodici]

Same with jet fuel on a plane. They calculate the amount to fuel carefully to be efficient but safe. Too much and the plane is heavier and uses more fuel. Too little and you might run out if put into a holding then diverted.

Obviously jet fuel is what it is it wont get more dense but a more efficient engine means less fuel needed means even more efficiency and so on.

[Swannie]

The Qantas 16h 45m flight from Dallas to Sydney aims for Brisbane, and then turns to Sydney as the plane approaches Australia. (10th longest commercial route in the world).

This allows the plane to land at Brisbane and refuel if the calculations are done wrong. Couldn't find stats on how many times it's had to land in BNE.

Pre-COVID, it was apparently common to try and off-load passengers to single stopover flights to reduce fuel needs (I was one of those passengers, and the crew confirmed it was a regular occurance).

[isolli]

It reminds me of this anecdote [0]:

An example is Singapore Airlines' former New York to Singapore flight, which could carry only 100 passengers (all business class) on the 10,300-mile (16,600 km) flight. According to an industry analyst, "It [was] pretty much a fuel tanker in the air."

[0] https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft

[crazygringo]

Knowing nothing about it, what causes fuel calculations to be done wrong?

Is it math errors, or uncertainty about exact weight of cargo and passengers, or wind conditions different from predicted, or something else?

[stenius]

Wind is the main one.

You might also run into some weather you didn't have to plan for and that changes the prevailing winds at the altitude you were previously cruising at or causes you to divert to fly around it.

[NovaDudely]

It was something I had never considered but it is wild to think about. I believe it was Vaclav Smil that highlighted it to me. On its longest trip an A380(I think?) takes off weighing 400 tons and lands weighing 200 tons. That kind of thing is just cool to ponder.

[arwhatever]

I realized while working on heavy transport aircraft that they their weight can be (very roughly) 1/3 aircraft, 1/3 fuel, and 1/3 cargo, and being struck by how different these proportions are from the family sedan.

[ryan93]

It is literally insane how much oil there is. Planes use i think less than 10% of world oil consumption.

[0xFF0123]

Rockets reaching orbit are an interesting example too.

[MaxMatti]

Not only that but too much might also cause you to have to dump fuel in order for the plane to be able to land.

[heywhatupboys]

0,01 % maybe

[nvy]

For a battery of arbitrary weight you need to spend the same amount of energy accelerating its mass, irrespective of how much energy that battery contains.

[mkaic]

Right, I believe GP's point is that for a given capacity, you now need fewer kilograms of batteries to store it, meaning the percentage of overall capacity used to accelerate the mass of the battery itself goes down.

[buro9]

The article mentions aircraft multiple times. Once a range is achieved through available energy, reducing weight is a goal. The energy is more useful the less weight you need to move as then you can shave off a bit more weight as less energy was needed.

Your car may not need this as much, an aircraft does.

[gibolt]

500-600 Wh/kg is the target for replacing average flight durations.

Fuel is one of the highest costs for an airline, so eliminating the majority of that will make the demand for any viable options go bananas, even with a much higher upfront cost.

Being seen as 'green' is a big bonus for the airline.

[baq]

If the tech takes off (pun intended) every major airport will need a SMR. Which is maybe good? But politically impractical today.

[regularfry]

Less of the "S". With current flight patterns you need multiple gigawatts. Calculations based on 737s leaving Gatwick:

Energy density of the fuel: 9.6kWh/L

900 flights per day = one flight every 96 seconds

26024.706L per flight

Total energy per flight: 9.6 x 26024.706kWh = 250MWh give or take = 900GJ

Total power supplied from Gatwick in the form of aviation fuel: 900GJ/96s = 9.375GW.

That's not only outside the range of SMRs, it's bigger than any single nuclear power station that's been built, by a comfortable margin.

To make electric flight work you can't think in terms of the way the current industry is structured because it's so distorted by the energy density of the current fuel.

[maccard]

That's assuming an overnight switch from what we have to all electric, for one of the busiest airports in the world.

Thinking in terms of disruption (from the innovator sense), their top 3 destinations [0] are Dublin, Barcelona and Malaga. Skipping barcelona becauese it's as busy, I don't think it's out of reach to consider that a 737 could do a return trip to dublin or Malaga without charging.

Another perspective is that taking off is significantly more energy intensive than cruising. According to [1], takeoff is equivalent to an hour of cruising. One way of looking at this is it only makes sense for mid haul travel instead. If we replaced transatlantic flights, or similar (us to Europe maybe) the savings would be immense and significantly more achievable

[0] https://www.gatwickairport.com/business-community/about-gatw...

[1] https://aviation.stackexchange.com/questions/47262/how-much-....

[baq]

Oof.

Jet engines are 35% efficient, I'd assume electric planes would be double that, does that change the calculation? Naively I'd say we 'only' need 4.5GW?

[mlsu]

With the energy efficiency attainable by traveling in the upper atmosphere, this might be the greenest possible long range transportation.

God such a tantalizing solar punk dream. I would love just to hear the inside of an electric commercial airliner at altitude.

[VBprogrammer]

Presumably they would use something like an electrically propelled ducted fan (basically the first stage of a high bypass engine). The noise I imagine would be reasonably similar.

[_puk]

I doubt it would be classical music and whale song playing over a beautifully calm scene..

More like kids watching movies without headphones, over loud conversations and screaming babies if other public transport is anything to go by.

But we can dream!

[oblio]

What's SMR?

[Flockster]

I would assume a Small Modular Reactor.

[daliusd]

Bicycles would benefit as well. I would love if my electric bicycle were slightly lighter.

[bluGill]

Most people should achieve far more weight loss from their belly than from their bike. But you can pay money to make the bike light and that is easier than working on yourself.

[AdrianB1]

Average plane cannot fly with batteries; the weight is still too high compared to jet fuel and the range is too short. Only short flights of up to 1000 km and 90 minutes will be in reach initially, jet fuel minus efficiency loses is still over 3000 Wh/kg, 6 times more than these new batteries.

[VilleOr]

Average US flight trip is about 800 km (~500 miles). If even half of all flights were powered by electricity, the impact on emissions would be huge.

[maccard]

Furthermore, the energy needed for takeoff is significantly higher than the energy for cruising. For an hour's flight, it's close to 50/50. The impact is disproportionately skewed towards shorter fkights

[zirgs]

Wondering if we could build devices that assist with takeoff - like it's done on aircraft carriers. Could save some energy that way.

[microjim]

Yes that’s correct. Probably a better way of articulating what I meant to say is that unlike adding more battery mass which gives you diminishing returns as that additional weight must be carried too, improvements in energy density give you gains closer to 1:1. Though in retrospect this isn’t a very interesting or insightful statement, hah.